Method and an apparatus for access network selection in visited network in a wireless communication system

ABSTRACT

A wireless communication system is disclosed. More particularly, access network selection scheme in visited network in a wireless communication system are disclosed. A method for selecting a Wireless Local Area Network (WLAN) access network by a user equipment (UE) in a visited network may comprise: determining, by the UE, if a selected WLAN access network in the visited network is available; updating, by the UE, a WLAN selection policy with a list of excluded WLAN access network, if the selected WLAN access network in the visited network is not available; and re-determining, by the UE, if there is an available WLAN access network in the visited network based on the updated WLAN selection policy.

CROSS-REFERENCE TO RELATED APPLICATIONS

Pursuant to 35 U.S.C. §119(e), this application claims the benefit ofU.S. Provisional Patent Application Ser. No. 61/769,134, filed on Feb.25, 2013, 61/804,163, filed on Mar. 21, 2013, 61/804,721, filed on Mar.24, 2013, and 61/806,949, filed on Apr. 1, 2013, the contents of whichare all hereby incorporated by reference herein in their entirety.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a wireless communication system, andmore particularly, to a method and an apparatus for access networkselection in visited network in a wireless communication system.

Discussion of the Related Art

Network environments may include a cellular access network (e.g., 3rdGeneration Partnership Project (3GPP) Global System for Mobilecommunication (GSM), Universal Mobile Telecommunication System (UMTS),Evolved Packet System (EPS), etc.) and a wireless local access network(WLAN). To fully and complementarily utilize a dual accessibility to thecellular access network and the WLAN, demands for dual mode terminalsare increasing.

Generally, a terminal in a visited network has multiple policies from ahome network and from the visited network, and uses the policy from thevisited network. However, if a terminal ends up with different visitednetworks in 3GPP access and WLAN access, it has been defined that theterminal could not use the policies from visited networks. Thus, for aterminal in such environment, access network selection mechanisms forselecting WLAN among accessible WLANs are based on the policy from thehome network.

The terminal may be allowed to be served by the WLAN access according tothe policy from the home network. Meanwhile, the policy of the visitednetwork is to restrict or forbid terminals being inbound roamers fromthe WLAN access. In this situation, there may be inconsistency or thevisited network may be forced to provide services to the terminal incontrast to its own policies.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a method and anapparatus for access network selection in visited network that obviatesone or more problems due to limitations and disadvantages of the relatedart.

An object of the present invention is to provide a method and anapparatus for access network selection in visited network to provideefficient usage of network resources and to provide enhanced userexperiences.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, amethod for selecting a Wireless Local Area Network (WLAN) access networkby a user equipment (UE) in a visited network may comprise: determining,by the UE, if a selected WLAN access network in the visited network isavailable; updating, by the UE, a WLAN selection policy with a list ofexcluded WLAN access network, if the selected WLAN access network in thevisited network is not available; and re-determining, by the UE, ifthere is an available WLAN access network in the visited network basedon the updated WLAN selection policy.

In another aspect of the present invention, provided herein is a userequipment (UE) for selecting a Wireless Local Area Network (WLAN) accessnetwork in a visited network may comprise: a transceiving module; and aprocessor. The processor may be configured: to determine if a selectedWLAN access network in the visited network is available; to update aWLAN selection policy with a list of excluded WLAN access network if theselected WLAN access network in the visited network is not available;and to re-determine if there is an available WLAN access network in thevisited network based on the updated WLAN selection policy.

The following matters are commonly applicable to the embodiments of thepresent invention.

The WLAN selection policy may be a WLAN selection policy provided by ahome network.

The list of excluded WLAN access network) may be provided by the visitednetwork.

The list of excluded WLAN access network may include identificationinformation of at least one WLAN access network.

The at least one WLAN access network may be configured as a forbiddenaccess or a restricted access.

The UE may determine that the selected WLAN access network in thevisited network is not available, if a request for connecting to theselected WLAN access network in the visited network is rejected.

The UE may receive a rejection message from the visited network, if therequest for connecting to the selected WLAN access network in thevisited network is rejected.

The list of excluded WLAN access network may be included in therejection message.

The determining step may be performed based on a WLAN selection policyof a home network.

The home network may be a home public land mobile network (HPLMN), andthe WLAN selection policy of the home network may be provided by a homeAccess Network Discovery and Selection Function (H-ANDSF).

The UE may have simultaneous connectivity to multiple VPLMNs, and havedifferent VPLMN in 3rd Generation Partnership Project (3GPP) access andWLAN access. The UE may not use a WLAN selection policy provided by aV-ANDSF of a VPLMN in the 3GPP access or a WLAN selection policyprovided by a V-ANDSF of a VPLMN in the WLAN access, but the UE may usea WLAN selection policy provided by the H-ANDSF, for the determiningstep.

The visited network may be a visited public land mobile network (VPLMN),and the WLAN selection policy of the visited network may be provided bya visited Access Network Discovery and Selection Function (V-ANDSF).

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 is a diagram showing the schematic architecture of an evolvedpacket system (EPS) which includes an evolved packet core (EPC);

FIG. 2 is a diagram illustrating a network structure of an evolveduniversal terrestrial radio access network (E-UTRAN) which connects toEPC.

FIG. 3 is a block diagram depicting architecture of a typical E-UTRANand a typical EPC.

FIGS. 4(a) and 4(b) are block diagrams depicting the user-plane protocoland the control-plane protocol stack for the E-UTRAN.

FIG. 5 is a diagram depicting structure of a physical channel.

FIG. 6 is a diagram illustrating a random access procedure for E-UTRANinitial access.

FIGS. 7(a) and 7(b) are block diagrams depicting architectures used foraccess network discovery and selection.

FIG. 8 and FIG. 9 show exemplary scenarios with different VPLMN in 3GPPaccess and WLAN access.

FIG. 10 is a flow diagram illustrating an exemplary method for accessnetwork selection in visited network according to the present invention.

FIG. 11 is a diagram showing the configuration of an apparatus accordingto an exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The following embodiments are proposed by combining constituentcomponents and characteristics of the present invention according to apredetermined format. The individual constituent components orcharacteristics should be considered to be optional factors on thecondition that there is no additional remark. If required, theindividual constituent components or characteristics may not be combinedwith other components or characteristics. Also, some constituentcomponents and/or characteristics may be combined to implement theembodiments of the present invention. The order of operations to bedisclosed in the embodiments of the present invention may be changed toothers. Some components or characteristics of any embodiment may also beincluded in other embodiments, or may be replaced with those of theother embodiments as necessary.

It should be noted that specific terms disclosed in the presentinvention are proposed for convenience of description and betterunderstanding of the present invention, and the use of these specificterms may be changed to another format within the technical scope orspirit of the present invention.

In some instances, well-known structures and devices are omitted inorder to avoid obscuring the concepts of the present invention and theimportant functions of the structures and devices are shown in blockdiagram form. The same reference numbers will be used throughout thedrawings to refer to the same or like parts.

The embodiments of the present invention can be supported by thestandard documents disclosed in any one of wireless access systems, suchas an IEEE 802 system, a 3^(rd) Generation Partnership Project (3GPP)system, a 3GPP Long Term Evolution (LTE) and LTE-A system, and a 3GPP2system. That is, the steps or portions, which are not described in orderto make the technical spirit of the present invention clear, may besupported by the above documents. In addition, all the terms disclosedin the present document may be described by the above standarddocuments.

The following technologies may be used in various wireless communicationsystems. For clarity, 3GPP LTE and 3GPP LTE-A will be focused upon inthe following description, but the scope of the present invention is notlimited thereto.

Terms used in the present specification are as follows.

-   -   UMTS (universal mobile telecommunication system): Third        generation mobile communication technology based on global        system for mobile communication (GSM) developed by 3GPP.    -   EPS (evolved packet system): Network system including an evolved        packet core (EPC) which is a packet switched (PS) core network        based on internet protocol (IP) and an access network such as        E-UTRAN, which is evolved from UTRAN.    -   NodeB: Base station of GERAN/UTRAN, which is mounted outdoors        and coverage of which forms a macro cell.    -   eNodeB: Base station of E-UTRAN, which is mounted outdoors and        coverage of which forms a macro cell.    -   UE: User equipment. The UE may be referred to as a terminal, a        mobile equipment (ME), a mobile station (MS), etc. In addition,        the UE may be a portable apparatus such as a laptop, a mobile        phone, a personal digital assistant (PDA), a smartphone and a        multimedia apparatus or a non-portable apparatus such as a        vehicle mounted apparatus.    -   Home NodeB (HNB): Base station of a UMTS network, which is        mounted indoors and coverage of which forms a micro cell.    -   Home eNodeB (HeNB): Base station of an EPS network, which is        mounted indoors and coverage of which forms a micro cell.    -   ANDSF (Access Network Discovery and Selection Function): The        ANDSF contains data management and control functionality        necessary to provide network discovery and selection assistance        data as per operators' policy. The ANDSF is able to initiate        data transfer to the UE, based on network triggers, and respond        to requests from the UE. It provides functions such as        inter-system mobility policy, access network discovery        information. The ANDSF in the subscriber's home operator network        may interact with other databases such as the HSS user profile        information residing in subscriber's home operator network. For        details on ANDSF, see 3GPP Technical Specification (TS) 23.402.    -   MME (mobility management entity): Network node of an EPS        network, which performs a mobility management (MM) function and        a session management (SM) function.    -   PDN-GW (packet data network-gateway)/PGW: Network node of an EPS        network, which performs a UE IP address allocation function, a        packet screening and filtering function and a charging data        collection function.    -   SGW (serving gateway): Network node of an EPS network, which        performs mobility anchor, packet routing, idle mode packet        buffering, triggering for enabling an MME to page a UE.    -   PCRF (policy and charging rule function): Network node of an EPS        network, which performs policy decision for dynamically applying        quality of service (QoS) and charging policy differentiated per        service flow.    -   OAM (operation administration and maintenance): OAM is a set of        network administration functions for providing network fault        display, performance information, data and diagnostic functions.    -   NAS (non-access stratum): Upper stratum of a control plane        between a UE and an MME. This is a functional layer for        signaling between a UE and a core network and exchanging a        traffic message in an LTE/UMTS protocol stack, supports UE        mobility, and supports a session management procedure for        establishing and maintaining an IP connection between a UE and a        PDN GW.    -   NAS configuration MO (NAS configuration management object): MO        used to configure parameters associated with NAS functionality        with respect to a UE.    -   PDN (packet data network): Network in which a server supporting        a specific service (e.g., a multimedia messaging service (MMS)        server, a wireless application protocol (WAP) server, etc.) is        located.    -   PDN connection: Logical connection between a UE and a PDN, which        is expressed by one IP address (one IPv4 address and/or one IPv6        prefix).    -   APN (Access Point Name): String indicating or identifying a PDN.        A requested service or a network (PDN) is accessed through a PGW        and the APN is the name (string) previously defined in the        network in order to find the PGW. For example, the APN may be        expressed by internet.mnc012.mcc345.gprs.    -   RAN (radio access network): Unit including a NodeB, an eNodeB        and a radio network controller for controlling the NodeB and the        eNodeB in a 3GPP network, which is present between UEs and        provides connection to a core network.    -   HLR (home location register)/HSS (home subscriber server):        Database having subscriber information in a 3GPP network. The        HSS may perform functions such as configuration storage,        identity management and user state storage.    -   PLMN (public land mobile network): Network configured for the        purpose of providing a mobile communication service to        individuals. This network may be configured on a per operator        basis.    -   NAS level congestion control: Congestion or overload control        function of an EPS network composed of APN based congestion        control and general NAS level mobility management control.    -   MM back-off timer (mobility management back-off timer): Mobility        management back-off timer used to control congestion when        congestion occurs in a network. While the MM back-off timer        runs, a UE is set so as not to perform attach, location        information update (e.g., tracking area update (TAU)), routing        area update (RAU), service request/extended service request,        etc. (in case of an emergency bearer service, a paging response        in an existing region, or a multimedia priority service (MPS),        even when the MM back-off timer runs, the UE is set to make a        request). Regarding operations related to a UE receiving MM        back-off timer (e.g., T3346), see 3GPP TS 23.401, TS 23.060, TS        24.301, TS 24.008.    -   SM back-off timer (session management back-off timer): Session        control back-off timer used to control congestion when        congestion occurs in a network. While the SM back-off timer        runs, a UE is set so as not to perform establishment or change        of a session based on an associated APN, etc. (in case of an        emergency bearer service or an MPS, even when the SM back-off        timer runs, the UE is set to make a request). Regarding        operations related to a UE receiving SM back-off timer (e.g.,        T3396), see 3GPP TS 23.401, TS 23.060, TS 24.301, TS 24.008.    -   TA (tracking area): Registration area of a UE in an EPS network.        The TA is identified by a tracking area identity (TAI).    -   RA (routing area): Registration area of a UE for a packet core        network domain in a GPRS/UMTS network. The RA is identified by a        routing area identity (RAI).

Hereinafter, a description will be given based on the above-describedterms.

FIG. 1 is a diagram showing the schematic architecture of an evolvedpacket system which includes an evolved packet core (EPC).

The EPC is a fundamental element of system architecture evolution (SAE)for improving 3GPP performance. SAE corresponds to a research projectfor deciding a network structure supporting mobility between varioustypes of networks. SAE aims to provide an optimized packet-based systemwhich supports various radio access technologies based on IP andprovides improved data transfer capabilities.

More specifically, the EPC is a core network of an IP mobilecommunication system for a 3GPP LTE system and may support apacket-based real-time and non-real-time service. In the existing mobilecommunication system (that is, a second or third generation mobilecommunication system), a core network function was implemented throughtwo distinct sub-domains of a voice network (a circuit-switched (CS)network) and a data network (a packet-switched (PS) network). In a 3GPPLTE system which is evolved from the third generation communicationsystem, sub-domains of a CS network and a PS network were unified intoone IP domain. That is, in a 3GPP LTE system, a UE having IP capabilityand a UE may be connected through an IP based base station (e.g., aneNodeB (evolved Node B)), an EPC, an application domain (e.g., an IMS)).That is, the EPC is a structure necessary to implement an end-to-end IPservice.

The EPC may include various components. FIG. 1 shows a serving gateway(SGW), a packet data network gateway (PDN GW), a mobility managemententity (MME), a serving GPRS (general packet radio service) supportingnode (SGSN) and an enhanced packet data gateway (ePDG).

The SGW operates as a boundary point between a radio access network(RAN) and a core network and is an element which performs a function formaintaining a data path between an eNodeB and a PDG GW. In addition, ifa UE moves over a region served by an eNodeB, the SGW serves as a localmobility anchor point. That is, packets may be routed through the SGWfor mobility in an evolved universal terrestrial radio access network(E-UTRAN) defined after 3GPP release-8. In addition, the SGW may serveas an anchor point for mobility of another 3GPP network (an RAN definedbefore 3GPP release-8, e.g., UTRAN or GERAN (global system for mobilecommunication (GSM)/enhanced data rates for global evolution (EDGE)radio access network).

The PDN GW corresponds to a termination point of a data interface for apacket data network. The PDN GW may support policy enforcement features,packet filtering and charging support. In addition, the PDN GW may serveas an anchor point for mobility management with a 3GPP network and anon-3GPP network (e.g., an untrusted network such as an interworkingwireless local area network (I-WLAN) and a trusted network such as acode division multiple access (CDMA) or WiMAX network).

Although the SGW and the PDN GW are configured as separate gateways inthe example of the network structure of FIG. 1, the two gateways may beimplemented according to a single gateway configuration option.

The MME performs signaling and control functions in order to supportaccess to network connection of a UE, network resource allocation,tracking, paging, roaming and handover. The MME controls control planefunctions associated with subscriber and session management. The MMEmanages numerous eNodeBs and signaling for selection of a conventionalgateway for handover to other 2G/3G networks. In addition, the MMEperforms security procedures, UE-to-network session handling, idle UElocation management, etc.

The SGSN handles all packet data such as mobility management andauthentication of a user for other 3GPP networks (e.g., GPRS networks).

The ePDG serves as a security node for a non-3GPP network (e.g., anI-WLAN, a Wi-Fi hotspot, etc.).

As described with reference to FIG. 1, a UE having IP capabilities mayaccess an IP service network (e.g., an IMS) provided by an operatorthrough various elements in the EPC based on 3GPP access or non-3GPPaccess.

FIG. 1 shows various reference points (e.g., S1-U, S1-MME, etc.). In the3GPP system, a conceptual link connecting two functions present indifferent functional entities of an E-UTRAN and an EPC is defined as areference point. Table 1 shows the reference points shown in FIG. 1. Inaddition to the example of Table 1, various reference points may bepresent according to network structure.

TABLE 1 Reference point Description S1-MME Reference point for thecontrol plane protocol between E-UTRAN and MME S1-U Reference pointbetween E-UTRAN and Serving GW for the per bearer user plane tunnelingand inter eNodeB path switching during handover S3 Reference pointbetween MME and SGSN. Enables user and bearer information exchange forinter 3GPP access network mobility in idle and/or active state. Thisreference point can be used intra-PLMN or inter-PLMN (e.g. in the caseof Inter-PLMN HO). S4 Reference between SGW and SGSN. Provides relatedcontrol and mobility support between GPRS Core and the 3GPP Anchorfunction of Serving GW. In addition, if Direct Tunnel is notestablished, it provides user plane tunneling. S5 Reference point forproviding user plane tunneling and tunnel management between Serving GWand PDN GW. Used for Serving GW relocation due to UE mobility and if theServing GW needs to connect to a non-co-located PDN GW for the requiredPDN connectivity. S11 Reference point between MME and SGW SGi Referencepoint between the PDN GW and the packet data network. Packet datanetwork may be an operator external public or private packet datanetwork or an intra operator packet data network, e.g. for provision ofIMS services. This reference point corresponds to Gi for 3GPP accesses.

Among the reference points shown in FIG. 1, S2a and S2b correspond to anon-3GPP interface. S2a is a reference point for providing associatedcontrol between the trusted non-3GPP access and the PDNGW and mobilitysupport to a user plane. S2b is a reference point for providingassociated control between the ePDG and the PDN GW and mobility supportto a user plane.

FIG. 2 is a diagram illustrating a network structure of an evolveduniversal terrestrial radio access network (E-UTRAN) which connects toEPC.

Universal mobile telecommunications system (UMTS) is a 3rd Generation(3G) asynchronous mobile communication system operating in wideband codedivision multiple access (WCDMA) based on European systems, globalsystem for mobile communications (GSM) and general packet radio services(GPRS). The long-term evolution (LTE) of UMTS has been developed by the3rd generation partnership project (3GPP) that standardized UMTS.

The 3GPP LTE is a technology for enabling high-speed packetcommunications. Many schemes have been proposed for the LTE objectiveincluding those that aim to reduce user and provider costs, improveservice quality, and expand and improve coverage and system capacity.The 3G LTE requires reduced cost per bit, increased serviceavailability, flexible use of a frequency band, a simple structure, anopen interface, and adequate power consumption of a UE as an upper-levelrequirement.

Referring to FIG. 2, the combination of E-UTRAN and EPC may be alsoreferred to as an LTE system or EPS. The communication network is widelydeployed to provide a variety of communication services such as voice(VoIP) through IMS and packet data.

As illustrated in FIG. 2, the EPS includes an evolved universalterrestrial radio access network (E-UTRAN), an Evolved Packet Core (EPC)and one or more user equipment. The E-UTRAN may include one or moreevolved NodeB (eNodeB) 20, and a plurality of user equipment (UE) 10 maybe located in one cell. One or more E-UTRAN mobility management entity(MME)/system architecture evolution (SAE) gateways 30 may be positionedat the end of the network and connected to an external network. SAEgateway includes SGW and PDN GW.

As used herein, “downlink” refers to communication from eNodeB 20 to UE10, and “uplink” refers to communication from the UE to an eNodeB. UE 10refers to communication equipment carried by a user and may be alsoreferred to as a mobile station (MS), a user terminal (UT), a subscriberstation (SS) or a wireless device.

An eNodeB 20 provides end points of a user plane and a control plane tothe UE 10. MME/SAE gateway 30 provides an end point of a session andmobility management function for UE 10. The eNodeB and MME/SAE gatewaymay be connected via an S1 interface.

The eNodeB 20 is generally a fixed station that communicates with a UE10, and may also be referred to as a base station (BS) or an accesspoint. One eNodeB 20 may be deployed per cell. An interface fortransmitting user traffic or control traffic may be used between eNodeBs20.

The MME provides various functions including NAS signalling to eNodeBs20, NAS signalling security, AS Security control, Inter CN nodesignalling for mobility between 3GPP access networks, Idle mode UEReachability (including control and execution of paging retransmission),Tracking Area list management (for UE in idle and active mode), PDN GWand Serving GW selection, MME selection for handovers with MME change,SGSN selection for handovers to 2G or 3G 3GPP access networks, Roaming,Authentication, Bearer management functions including dedicated bearerestablishment, Support for PWS (which includes ETWS and CMAS) messagetransmission. The SAE gateway host provides assorted functions includingPer-user based packet filtering (by e.g. deep packet inspection), LawfulInterception, UE IP address allocation, Transport level packet markingin the downlink, UL and DL service level charging, gating and rateenforcement, DL rate enforcement based on APN-AMBR. For clarity MME/SAEgateway 30 will be referred to herein simply as a “gateway,” but it isunderstood that this entity includes both an MME and an SAE gateway.

A plurality of nodes may be connected between eNodeB 20 and gateway 30via the S1 interface. The eNodeBs 20 may be connected to each other viaan X2 interface and neighboring eNodeBs may have a meshed networkstructure that has the X2 interface.

FIG. 3 is a block diagram depicting architecture of a typical E-UTRANand a typical EPC.

As illustrated, eNodeB 20 may perform functions of selection for gateway30, routing toward the gateway during a Radio Resource Control (RRC)activation, scheduling and transmitting of paging messages, schedulingand transmitting of Broadcast Channel (BCCH) information, dynamicallocation of resources to UEs 10 in both uplink and downlink,configuration and provisioning of eNodeB measurements, radio bearercontrol, radio admission control (RAC), and connection mobility controlin LTE ACTIVE state. In the EPC, and as noted above, gateway 30 mayperform functions of paging origination, LTE-IDLE state management,ciphering of the user plane, System Architecture Evolution (SAE) bearercontrol, and ciphering and integrity protection of Non-Access Stratum(NAS) signaling.

FIGS. 4(a) and 4(b) are block diagrams depicting the user-plane protocoland the control-plane protocol stack for the E-UMTS.

As illustrated, the protocol layers may be divided into a first layer(L1), a second layer (L2) and a third layer (L3) based upon the threelower layers of an open system interconnection (OSI) standard model thatis well known in the art of communication systems.

The physical layer, the first layer (L1), provides an informationtransmission service to an upper layer by using a physical channel. Thephysical layer is connected with a medium access control (MAC) layerlocated at a higher level through a transport channel, and data betweenthe MAC layer and the physical layer is transferred via the transportchannel. Between different physical layers, namely, between physicallayers of a transmission side and a reception side, data is transferredvia the physical channel.

The MAC layer of Layer 2 (L2) provides services to a radio link control(RLC) layer (which is a higher layer) via a logical channel. The RLClayer of Layer 2 (L2) supports the transmission of data withreliability. It should be noted that the RLC layer illustrated in FIGS.4(a) and 4(b) is depicted because if the RLC functions are implementedin and performed by the MAC layer, the RLC layer itself is not required.The PDCP layer of Layer 2 (L2) performs a header compression functionthat reduces unnecessary control information such that data beingtransmitted by employing Internet protocol (IP) packets, such as IPv4 orIPv6, can be efficiently sent over a radio (wireless) interface that hasa relatively small bandwidth.

A radio resource control (RRC) layer located at the lowest portion ofthe third layer (L3) is only defined in the control plane and controlslogical channels, transport channels and the physical channels inrelation to the configuration, reconfiguration, and release of the radiobearers (RBs). Here, the RB signifies a service provided by the secondlayer (L2) for data transmission between the UE and the UTRAN.

As illustrated in FIG. 4(a), the RLC and MAC layers (terminated in aneNodeB 20 on the network side) may perform functions such as Scheduling,Automatic Repeat Request (ARQ), and Hybrid Automatic Repeat Request(HARQ). The PDCP layer (terminated in eNodeB 20 on the network side) mayperform the user plane functions such as header compression, integrityprotection, and ciphering.

As illustrated in FIG. 4(b), the RLC and MAC layers (terminated in aneNodeB 20 on the network side) perform the same functions for thecontrol plane. As illustrated, the RRC layer (terminated in an eNodeB 20on the network side) may perform functions such as broadcasting, paging,RRC connection management, Radio Bearer (RB) control, mobilityfunctions, and UE measurement reporting and controlling. The NAS controlprotocol (terminated in the MME of gateway 30 on the network side) mayperform functions such as a SAE bearer management, authentication, LTEIDLE mobility handling, paging origination in LTE IDLE, and securitycontrol for the signaling between the gateway and UE 10.

The RRC state may be divided into two different states such as aRRC_IDLE and a RRC_CONNECTED. In RRC_IDLE state, the UE 10 may receivebroadcasts of system information and paging information while the UEspecifies a Discontinuous Reception (DRX) configured by NAS, and the UEhas been allocated an identification (ID) which uniquely identifies theUE in a tracking area and may perform PLMN selection and cellre-selection. Also, in RRC-IDLE state, no RRC context is stored in theeNodeB.

In RRC_CONNECTED state, the UE 10 has an E-UTRAN RRC connection and acontext in the E-UTRAN, such that transmitting and/or receiving datato/from the network (eNodeB) becomes possible. Also, the UE 10 mayreport channel quality information and feedback information to theeNodeB.

In RRC_CONNECTED state, the E-UTRAN knows the cell to which the UE 10belongs. Therefore, the network may transmit and/or receive data to/fromUE 10, the network may control mobility (handover and inter-Radio AccessTechnology (inter-RAT) cell change order to GERAN with Network AssistedCell Change (NACC)) of the UE, and the network may perform cellmeasurements for a neighboring cell.

In RRC_IDLE mode, the UE 10 specifies the paging DRX (DiscontinuousReception) cycle. Specifically, the UE 10 monitors a paging signal at aspecific paging occasion of every UE specific paging DRX cycle.

The paging occasion is a time interval during which a paging signal istransmitted. The UE 10 has its own paging occasion.

A paging message is transmitted over all cells belonging to the sametracking area. If the UE 10 moves from one tracking area to anothertracking area, the UE will send a tracking area update message to thenetwork to update its location.

FIG. 5 is a diagram depicting structure of a physical channel.

A physical channel transfers signaling and data between layer L1 of a UEand eNB. As illustrated in FIG. 5, the physical channel transfers thesignaling and data with a radio resource, which consists of one or moresub-carriers in frequency and one more symbols in time.

One sub-frame, which is 1.0 ms. in length, consists of several symbols.The particular symbol(s) of the sub-frame, such as the first symbol ofthe sub-frame, may be used for downlink control channel (PDCCH). PDCCHcarries dynamic allocated resources, such as PRBs and MCS.

A transport channel transfers signaling and data between the L1 and MAClayers. A physical channel is mapped to a transport channel.

Downlink transport channel types include a Broadcast Channel (BCH), aDownlink Shared Channel (DL-SCH), a Paging Channel (PCH) and a MulticastChannel (MCH). The BCH is used for transmitting system information. TheDL-SCH supports HARQ, dynamic link adaptation by varying the modulation,coding and transmit power, and both dynamic and semi-static resourceallocation. The DL-SCH also may enable broadcast in the entire cell andthe use of beamforming. The PCH is used for paging a UE. The MCH is usedfor multicast or broadcast service transmission.

Uplink transport channel types include an Uplink Shared Channel (UL-SCH)and Random Access Channel(s) (RACH). The UL-SCH supports HARQ anddynamic link adaptation by varying the transmit power and potentiallymodulation and coding. The UL-SCH also may enable the use ofbeamforming. The RACH is normally used for initial access to a cell.

The MAC sublayer provides data transfer services on logical channels. Aset of logical channel types is defined for different data transferservices offered by MAC. Each logical channel type is defined accordingto the type of information transferred.

Logical channels are generally classified into two groups. The twogroups are control channels for the transfer of control planeinformation and traffic channels for the transfer of user planeinformation.

Control channels are used for transfer of control plane informationonly. The control channels provided by MAC include a Broadcast ControlChannel (BCCH), a Paging Control Channel (PCCH), a Common ControlChannel (CCCH), a Multicast Control Channel (MCCH) and a DedicatedControl Channel (DCCH). The BCCH is a downlink channel for broadcastingsystem control information. The PCCH is a downlink channel thattransfers paging information and is used when the network does not knowthe location cell of a UE. The CCCH is used by UEs having no RRCconnection with the network. The MCCH is a point-to-multipoint downlinkchannel used for transmitting MBMS control information from the networkto a UE. The DCCH is a point-to-point bi-directional channel used by UEshaving an RRC connection that transmits dedicated control informationbetween a UE and the network.

Traffic channels are used for the transfer of user plane informationonly. The traffic channels provided by MAC include a Dedicated TrafficChannel (DTCH) and a Multicast Traffic Channel (MTCH). The DTCH is apoint-to-point channel, dedicated to one UE for the transfer of userinformation and may exist in both uplink and downlink. The MTCH is apoint-to-multipoint downlink channel for transmitting traffic data fromthe network to the UE.

Uplink connections between logical channels and transport channelsinclude a DCCH that may be mapped to UL-SCH, a DTCH that may be mappedto UL-SCH and a CCCH that may be mapped to UL-SCH. Downlink connectionsbetween logical channels and transport channels include a BCCH that maybe mapped to BCH or DL-SCH, a PCCH that may be mapped to PCH, a DCCHthat may be mapped to DL-SCH, and a DTCH that may be mapped to DL-SCH, aMCCH that may be mapped to MCH, and a MTCH that may be mapped to MCH.

It is known that different cause values may be mapped on the signaturesequence used to send messages between a UE and eNB and that eitherChannel Quality Indicator (CQI) or path loss and cause or message sizeare candidates for inclusion in the initial preamble.

FIG. 6 is a diagram illustrating a random access procedure for E-UTRANinitial access.

FIG. 6 illustrates different messages exchanged between a UE and eNBduring initial access. When a UE wishes to access the network anddetermines a message to be transmitted, the message may be linked to apurpose and a cause value may be determined. The size of the idealmessage number 3 illustrated in FIG. 6 may also be determined byidentifying all optional information and different alternative sizes,such as by removing optional information, or an alternative “schedulingrequest” message may be used.

The UE acquires necessary information for the transmission of thepreamble, UL interference, Pilot Transmit power and requiredSignal-to-Noise Ratio (SNR) for the preamble detection at the receiveror combinations thereof. This information must allow the calculation ofthe initial transmit power of the preamble. It is beneficial to transmitthe uplink message in the vicinity of the preamble from a frequencypoint of view in order to ensure that the same channel is used for thetransmission of the message.

The UE should take into account the uplink interference and the uplinkpath loss in order to ensure that the network receives the preamble witha minimum SNR. The uplink interference may be determined only in theeNodeB and, therefore, must be broadcast by the eNodeB and received bythe UE prior to the transmission of the preamble. The uplink path lossmay be considered to be similar to the downlink path loss and may beestimated by the UE from the received Rx (receiver) signal strength whenthe transmit power of some pilot sequence of the cell is known to theUE.

The required uplink SNR for the detection of the preamble wouldtypically depend on the eNodeB configuration, such as a number of Rxantennas and receiver performance. There may be advantages totransmitting the rather static Transmit power of the pilot and thenecessary uplink SNR separately form the varying uplink interference andpossibly the power offset required between the preamble and the message.

The initial transmission power of the preamble may be roughly calculatedaccording to the following formula: [Transmitpower=TransmitPilot−RxPilot+ULinterference+Offset+SNRRequired].

Therefore, any combination of SNRRequired, ULinterference, TransmitPilotand Offset may be broadcast. In principle, only one value must bebroadcast. This is essentially the method in current UMTS systems,although the UL interference in LTE will mainly be neighboring cellinterference that is probably more constant than in UMTS.

The UE determines the initial uplink transmit power for the transmissionof the preamble as explained above. The receiver in the eNB is able toestimate the absolute received power as well as the relative receivedpower compared to the interference in the cell. The eNB will consider apreamble detected if the received signal power compared to theinterference is above an eNB known threshold.

The UE performs power ramping in order to ensure that a UE may bedetected even if the initially estimated transmission power for thepreamble is not adequate. Another preamble will most likely betransmitted if no acknowledgement or a negative acknowledgement isreceived by the UE before the next random access attempt. The transmitpower of the preamble may be increased, and/or the preamble may betransmitted on a different uplink frequency in order to increase theprobability of detection. Therefore, the actual transmit power of thepreamble that will be detected does not necessarily correspond to theinitial transmit power of the preamble as initially calculated by theUE.

The UE must determine the possible uplink transport format The transportformat, which may include Modulation and Coding Scheme (MCS) and anumber of resource blocks that should be used by the UE, depends mainlyon two parameters, specifically the SNR at the eNB and the required sizeof the message to be transmitted.

In practice, a maximum UE message size, or payload, and a requiredminimum SNR correspond to each transport format. In UMTS, the UEdetermines before the transmission of the preamble whether a transportformat can be chosen for the transmission according to the estimatedinitial preamble transmit power, the required offset between preambleand the transport block, the maximum allowed or available UE transmitpower, a fixed offset and additional margin. The preamble in UMTS neednot contain any information regarding the transport format selected bythe UE since the network does not need to reserve time and frequencyresources and, therefore, the transport format is indicated togetherwith the transmitted message.

The eNB must be aware of the size of the message that the UE intends totransmit and the SNR achievable by the UE in order to select the correcttransport format upon reception of the preamble and then reserve thenecessary time and frequency resources. Therefore, the eNB cannotestimate the SNR achievable by the UE according to the received preamblebecause the UE transmit power compared to the maximum allowed orpossible UE transmit power is not known to the eNB, given that the UEwill most likely consider the measured path loss in the downlink or someequivalent measure for the determination of the initial preambletransmission power.

The eNB could calculate a difference between the path loss estimated inthe downlink compared and the path loss of the uplink. However, thiscalculation is not possible if power ramping is used and the UE transmitpower for the preamble does not correspond to the initially calculatedUE transmit power. Furthermore, the precision of the actual UE transmitpower and the transmit power at which the UE is intended to transmit isvery low. Therefore, it has been proposed to code the path loss or CQIestimation of the downlink and the message size or the cause value inthe uplink in the signature.

FIGS. 7(a) and 7(b) are block diagrams depicting architectures used foraccess network discovery and selection.

FIG. 7(a) illustrates a non-roaming architecture for Access NetworkDiscovery and Selection Functions (ANDSF). FIG. 7(b) illustrates aroaming architecture for ANDSF.

The architecture is based on a new network element called Access NetworkDiscovery and Selection Function (ANDSF). An ANDSF element located inthe home PLMN (HPLMN) of a UE is referred to as the Home-ANDSF (H-ANDSF)for this UE, whereas an ANDSF element located in the visited PLMN(VPLMN) of a UE is referred to as the Visited-ANDSF (V-ANDSF) for thisUE. Unless otherwise specified, the term ANDSF is used to refer to bothan H-ANDSF and a V-ANDSF. In the examples of FIGS. 7(a) and 7(b), thesupport and the use of these functions and interfaces are optional.

Access Network Selection

In this document, the term “a cellular access network” may refer to acellular radio access network or a core network such as EPC. A cellularaccess network may be exemplified by, but not limited to a 3GPP accessnetwork such as GERAN, UTRAN, E-UTRAN, or a 3GPP2 access network such asCDMA1×, HRPD.

WLAN access network may be exemplified by, but not limited to a WLANaccess network according to 802.11 series, or Hotspot 2.0.

A dual mode terminal may support accessibility to both of a cellularaccess network and a WLAN. The term “a dual mode terminal” may refer toa terminal having a capability of routing traffic (e.g. IP traffic)simultaneously to a cellular access network and to a WLAN accessnetwork, or a terminal having a capability of routing traffic either toa cellular access network or to a WLAN access network.

Standardization of WLAN Network Selection for 3GPP Terminals (WLAN NS)are developing as a work item of 3GPP Release-12. WLAN NS studiessolutions for enhanced WLAN network selection for a dual mode terminalsupporting a cellular access network and a WLAN access network.

One of key issues of WLAN NS is a simultaneous connectivity to multipleVPLMNs. For a terminal being simultaneously connected to multipleVPLMNs, it is required to determine a policy to be applied for aterminal in a visited network (e.g., a terminal in roaming state).

As described in TS 24.234, the network and PLMN selection in WLAN isindependent if PLMN selection that is performed in 3GPP access: “Networkselection procedure is completely independent of the result of the PLMNselection under other radio access technologies that are specified in3GPP TS 23.122”. There is thus the possibility that a UE simultaneouslyconnected to both 3GPP access and WLAN access selects different VPLMN inthe two accesses.

For the case of ePDG selection, the procedures defined in TS 24.302 andTS 23.402 can result in one of the following options: i) If the UE isattached to a VPLMN in 3GPP access, the UE may either find an ePDG inthe VPLMN used in 3GPP access or an ePDG in HPLMN; ii) If the UE isattached to HPLMN in 3GPP access, the UE finds an ePDG in HPLMN; iii) Ifthe UE is not attached in 3GPP access, the UE may either find an ePDG inthe VPLMN selected in WLAN access or an ePDG in HPLMN. The ePDGselection procedure can result in an ePDG located in VPLMN selected for3GPP access, in VPLMN selected for WLAN access or in HPLMN.

FIG. 8 and FIG. 9 show exemplary scenarios with different VPLMN in 3GPPaccess and WLAN access.

Referring to FIG. 8, the UE ends up with different VPLMN in 3GPP accessand WLAN access. This scenario may happen when UE attaches in both 3GPPand WLAN access and the PLMN selection procedures end up in separateVPLMN (e.g., in SaMOG (S2a Mobility based on GPRS Tunneling Protocol(GTP) and WLAN access to the EPC network) case).

Referring to FIG. 9, the UE ends up with different VPLMN in 3GPP accessand WLAN access, and ePDG selected in 3GPP VPLMN. This scenario mayhappen when UE first attaches in 3GPP, then attaches in WLAN access andthen finds an ePDG in 3GPP VPLMN.

The scenario with multiple simultaneous serving PLMNs has not beensufficiently addressed in 3GPP. For a roaming UE in such a scenario,issues that may need further resolution include: i) Is the scenariodescribed above valid or should it be avoided, e.g. by appropriatespecification changes? ii) Even though mobility and routing policiesfrom H-ANDSF should as of today not impact the PLMN selectionprocedures, it is not clear if policies from H-ANDSF policies applysince an access change would also result in PLMN change. It is not clearif policies from any of the two V-ANDSFs can apply in such a scenario.

Therefore, there is a need to clarify (V-)ANDSF usage (e.g. which ANDSFis used at each mobility/selection step) and other aspects related toscenarios where a UE is served by different VPLMN in 3GPP access andWLAN access.

Recently, Technical Report (TR) 23.865v0.5.0 provides a solution for theaforementioned usage of ANDSF policies in (V)-PLMN.

An ANDSF server provides policy towards a given UE in order for that UEto be able to use more extensive decision-making criteria whendetermining which access the UE should connect to.

A V-ANDSF server associated with a given VPLMN could be used to downloadaccess network selection policies to determine the best access networkassociated to a given VPLMN. This implies that a V-ANDSF server,belonging to Operator X, may provide policies towards a UE belonging toOperator Y. The current solution is that the UE reconciles the policiesfrom V-ANDSF and H-ANDSF and, if there is overlap, gives precedence topolicies from the V-ANDSF.

As described in the key issue of the simultaneous connectivity tomultiple VPLMNs, the UE may be connected to two different VPLMNssimultaneously, one in 3GPP access and one in WLAN access. For thesescenarios the UE may potentially receive policies from two V-ANDSFservers, one in each VPLMN. It is not clear which V-ANDSF, if any, shallbe used for the policy information or if one of the V-ANDSF servers hasprecedence over the other one.

As per proposed solution, 3GPP system will be enhanced to allow theV-ANDSF policies to be taken into account for the case when both 3GPPand non-3GPP accesses connect via the same VPLMN. For this solution, theUE in case of the simultaneous connectivity to multiple VPLMNs as inFIG. 8 could not use the V-ANDSF in VPLMN1 or VPLMN2, while the UE incase of the simultaneous connectivity to multiple VPLMNs as in FIG. 9could use the V-ANDSF for both accesses in VPLMN1. The UE can acceptpolicies received from the V-ANDSF server only if the UE has singleselected VPLMN for all attached accesses.

The above solution still requires refinement taking into account aninconsistency between policies from V-ANDSF and H-ANDSF. Conventionally(i.e., before 3GPP release-12), in case of connectivity to a singleVPLMN, a UE uses or prioritizes a policy from the V-ANDSF if the UEreceives both of a policy from H-ANDSF (e.g., a policy configured byHPLMN to the UE, or a policy received by the UE from the H-ANDSF) and apolicy from V-ANDSF. In case of simultaneous connectivity to multipleVPLMNs, if a UE has different VPLMN in 3GPP access and WLAN access, theUE could not use the V-ANDSF in VPLMN1 or VPLMN2, but should use theH-ANDSF. In this case, inconsistency between policies from V-ANDSF andH-ANDSF may cause a problem in a visited network.

For example, it may be assumed a situation that a roaming UE (i.e., a UE(or a user, or a subscriber) in visited network) has simultaneousconnectivity to VPLMN1 and VPLMN2 and is connected to a WLAN access, anda V-ANDSF of one of the multiple VPLMNs which operates the WLAN access(e.g., VPLMN1 to which the WLAN access belongs) provides a policy thatthe WLAN access is set as restricted access or forbidden, while aH-ANDSF of a HPLMN of the UE provides a policy that there is norestriction for WLAN access. The restricted access or the forbiddenaccess is defined as the Table 2 for all WLAN access networks or aspecific WLAN access network. In table 2, values are forAccessNetworkPriority leaf as defined in TS 24.312.

TABLE 2 Value Description  0 Reserved  1-250 Priority value 251-253Reserved 254 Restricted access. This access should be avoided if thecurrent rule is active. 255 Forbidden. UE is not allowed to use thisaccess if the current rule is active.

In this situation, according to the conventional solution, the UE couldnot use the V-ANDSF in VPLMN1 or VPLMN2, but uses the H-ANDSF, thus theUE is allowed to be served by the WLAN access. VPLMN1, which restrictsor forbids the UE from the WLAN access, should provide services to theUE in contrast to its own policies.

Such exemplary situation may be occurred when the VPLMN1 has WLAN#1,WLAN#2 and WLAN#3, and makes a policy that only the subscribers to itsown PLMN are allowed to use or access the WLAN#1, WLAN#2 and WLAN#3 butinbound roamers are considered as restricted or forbidden to use oraccess the WLAN#1, WLAN#2 and WLAN#3. In addition, information onrestricted or forbidden access for the WLAN#1, WLAN#2 and WLAN#3 arereflected to a policy of an ANDSF of VPLMN1, but are not yet reflectedto a policy of an ANDSF of other PLMNs (including HPLMN of the inboundroamer to the VPLMN1).

To address such inconsistency between policies of inconsistency betweenpolicies from V-ANDSF and H-ANDSF, for example in case of simultaneousconnectivity to multiple VPLMNs, an advanced mechanism of access networkselection is proposed. Various embodiments of the proposed mechanismwill be described.

One or more of the embodiments may be applied independently or incombination, for a UE currently connected to (hereinafter, “connect to”may refer to “associate with” or “having an access to” unless describedotherwise) a WLAN access network of a visited network (e.g., VPLMN1), orfor a UE being about to connect to a WLAN access network (i.e., anavailable WLAN access network) of the VPLMN1. In addition, it is assumedthat the UE (e.g., a dual mode terminal) is connected to a cellularaccess network of the VPLMN1, or is connected to a cellular accessnetwork of another VPLMN (e.g., VPLMN2). It is also assumed that the UEhas received or has not received a policy from V-ANDSF of the VPLMN1when applying the following embodiments.

Embodiment 1

If a policy provided by a V-ANDSF of the VPLMN1 indicates that thecurrently connected WLAN access network or an available WLAN accessnetwork (or a WLAN access network which has selected to associate) is aforbidden access (or a not-allowed access), the UE uses (or applies, orfollows) a policy provided by the V-ANDSF.

If a policy provided by a V-ANDSF of the VPLMN1 indicates that thecurrently connected WLAN access network or an available WLAN accessnetwork (or a WLAN access network which has selected to associate) is arestricted access (or an avoided access), the UE uses (or applies, orfollows) a policy provided by the V-ANDSF.

Consequently, the UE may perform at least one of the followingoperations i)-iv) for IP flow(s) and/or PDN connection(s) which is to beserved using the WLAN access network.

i) The UE may select another WLAN access network of the same PLMN as thecurrently connected WLAN access network or an available WLAN accessnetwork (or a WLAN access network which has selected to associate).

ii) The UE may select another WLAN access network of a PLMN differentfrom the PLMN of the currently connected WLAN access network or anavailable WLAN access network (or a WLAN access network which hasselected to associate).

iii) The UE may select another type of access network or accesstechnology (e.g., 3GPP access network). For example, the UE may select3GPP access network to which the UE is connected.

iv) The UE may maintain connection to the WLAN access network to whichthe UE is already connected. In addition, at a point of time when the UEcannot be served by the WLAN access network or when the UE should applya policy related to access network selection, the UE uses (or applies,or follows) a policy provided by the V-ANDSF of VPLMN1.

The policy provided by the V-ANDSF of the VPLMN1 may include informationindicating whether the UE should immediately release connection to theWLAN access network (e.g., applying the operation of i), ii) or iii)) orthe UE is allowed to maintain the WLAN access network for a while (e.g.,applying the operation of iv)), when the WLAN access network or theavailable WLAN access network (or a WLAN access network which hasselected to associate) is configured as restricted access or forbiddenaccess by the VPLMN1.

The UE may perform at least one of the following operations of a)-e),when the UE uses (or applies, or follows) a policy provided by theV-ANDSF of VPLMN1. In addition, implicit or explicit information being abasis of determining or using the at least one of operations of a)-e)may be provided by the H-ANDSF and/or the V-ANDSF. Additionally oralternatively, information being a basis of determining or using the atleast one of operations of a)-e) may be configured with the UE.

a) The UE may apply the policy provided by the V-ANDSF to any type ofaccess network selection or any type of access technology selection.

b) The UE may apply the policy provided by the V-ANDSF only to WLANaccess network selection. For other types of access network selection(e.g., 3GPP access network selection), the UE may apply a policyprovided by the H-ANDSF, or apply a policy provided by a V-ANDSF of aVPLMN to which a UE-connected 3GPP access network belongs.

c) The UE may use the policy provided by the V-ANDSF only for thepurpose of checking if the currently connected WLAN access network or anavailable WLAN access network (or a WLAN access network which hasselected to associate) is configured as a restricted access/a forbiddenaccess. Here, the UE may basically use a policy provided by the H-ANDSFor a policy provided by a V-ANDSF of a VPLMN to which a UE-connected3GPP access network belongs. For example, the UE basically uses thepolicy provided by the H-ANDSF, and if the policy from the H-ANDSFindicates that a WLAN access network is preferred for an IP flow#1, thenthe UE attempts to connect to a WLAN access network. If the UE attemptsto connect to WLAN#1 of VPLMN1, the UE may use the policy from theV-ANDSF of VPLMN1 to check if the WLAN#1 is configured as a forbiddenaccess or a restricted access for the UE. Additionally, the UE mayattempt to connect to a WLAN access network in another PLMN (e.g.,VPLMN2) to which a UE-connected 3GPP access network belongs. In thiscase, the UE basically follows the policy from the H-ANDSF, and uses thepolicy from the V-ANDSF of the VPLMN2 to check if the connected WLANaccess network or an available WLAN access network is configured as aforbidden access or a restricted access for the UE. To sum, in case aPLMN that provides the UE with the policy that the UE basically followsand a PLMN to which a UE-connected/selected/available WLAN(s) for WLANaccess network selection belongs are different, the UE may use thepolicy provided by the PLMN to which the UE-connected/selected/availableWLAN(s) belongs for checking the candidate WLAN(s) is configured as aforbidden access or a restricted access for the UE.

d) The UE may use a policy provided by the H-ANDSF for WLAN accessselection (e.g., information related to prioritized access orinformation related to WLAN preference), while using a policy providedby the V-ANDSF (e.g., information related to prioritized access orinformation related to WLAN preference) to check if theUE-connected/selected/available WLAN access network is a forbiddenaccess or a restricted access for the UE. For other matters, the policyfrom the H-ANDSF and the policy from the V-ANDSF may be used or appliedin various forms of combination. The information related to prioritizedaccess or the information related to WLAN preference may includeinformation related to prioritized access, preferred access, restrictedaccess and/or forbidden access.

e) The UE may basically use a policy provided by the H-ANDSF. If thereare not any available/selectable WLAN access networks according to thepolicy provided by the H-ANDSF, then the UE may use a policy provided bythe V-ANDSF for WLAN access network selection.

For a UE-connected/selected/available WLAN access network, a restrictedaccess configuration or a forbidden access configuration may be static,or may be dynamic according to a condition of the network. For example,V-ANDSF may configure a WLAN access network as forbidden access in caseof the WLAN access network being overloaded or congested. If the WLANaccess network is not overloaded or congested any more, the V-ANDSF mayrelease the forbidden access configuration or may configure the WLANaccess network as an available access or a prioritized access.

In addition, if the UE selects a WLAN access network belongs to a VPLMN,before connecting to (or associating with) the WLAN access network, theUE may perform operations to obtain policy (or related information) froma V-ANDSF of the VPLMN to which the WLAN access network belongs.

Embodiment 2

When a UE requests authentication/authorization during attempting toconnect to a WLAN access network, an AAA(Authentication/Authorization/Accounting) proxy server of a VPLMN towhich the WLAN access network belongs may respond with a rejection (or arefusal to accept, or a failure) in response to a request forauthentication/authorization. Consequently, the UE may not connect tothe WLAN access network.

The AAA proxy server may include a reject code (or an error code, or aresult code, or a cause) information in a response message in order toprevent the UE from connecting to the WLAN access network. Accordingly,the UE received the response message may not attempt to re-connect theWLAN access network.

Additionally or alternatively, the AAA proxy server may include, in aresponse message, information on a list of WLAN access network(s) whichshould be excluded or prohibited from a WLAN access network selectionamong WLAN access networks of a PLMN to which the AAA proxy serverbelongs. The information on the excluded WLAN access network(s) mayinclude a WLAN access network(s) configured as a forbidden access forthe UE, and/or a WLAN access network(s) configured as a restrictedaccess for the UE. The UE received the information on the excluded WLANaccess network(s) may not attempt to connect to or re-connect to theexcluded WLAN access network(s). The UE may store the information on theexcluded WLAN access network(s) or information on therejected/refused/failed WLAN access networks(s).

The response message from the AAA proxy server may be delivered to theUE as it is or in a modified form via the WLAN access network (or atrusted WLAN access network including the WLAN access network, or anuntrusted non-3GPP access network including the WLAN access network).

AAA proxy server may determine to reject a request for connection to theWLAN access network of the UE based on one or more of the followinginformation, but not limited thereto.

-   -   Whether the WLAN access network to which the UE/subscriber/user        is connected or is about to connect is a forbidden access for        the UE/subscriber/user.    -   Whether WLAN access network to which the UE/subscriber/user is        connected or is about to connect is a restricted access for the        UE/subscriber/user.    -   Local policy, operator's policy, local information, local        configuration.    -   Access Network Identity (ANID) information (e.g., information        indicating whether an access network corresponding to the ANID        is WLAN access network or not) provided in a request for        authentication/authorization (or included in a request message        for authentication/authorization).    -   Access Type information (e.g., information indicating whether        the Access Type of an access network is WLAN access network or        not) provided in a request for authentication/authorization (or        included in a request message for authentication/authorization).    -   ID information of a WLAN access network provided in a request        for authentication/authorization (or included in a request        message for authentication/authorization).    -   Non-Seamless WLAN Offload (NSWO) related information (e.g.,        information indicating whether a trusted WLAN access network        (TWAN) supports NSWO or not) provided in a request for        authentication/authorization (or included in a request message        for authentication/authorization).    -   ID information of the UE/subscriber/user.    -   Subscription information.    -   Roaming agreement information with a HPLMN of the UE.    -   Load/overload/congestion status information of a WLAN access        network to which the UE/subscriber/user is connected or is about        to connect.    -   Load/overload/congestion status information of all connectable        (or associable, or available) WLAN access network(s).

As described above, the UE selects or reselects a WLAN access networkbased on a WLAN selection policy which includes a list of excluded orprohibited WLAN access network(s). The list of excluded or prohibitedWLAN access network(s) may be provided to the UE from or via a networknode which generates, stores or delivers policy information, such as AAAproxy, ANDSF, PCRF and so on.

The UE may be in roaming state (or in a visited network) when applyingthe WLAN selection mechanism using the list of excluded or prohibitedWLAN access network(s). The list of excluded or prohibited WLAN accessnetwork(s) may include identifier(s) (e.g., service setidentification(s), SSID(s)) of the WLAN access network(s) not preferredfor selection/reselection.

The WLAN selection policy is a set of operator-defined rules thatdetermines how the UE selects and reselects a WLAN access network. AWLAN access network selection criterion may take into account the listof excluded or prohibited WLAN access network(s).

The UE may be provisioned with multiple valid WLAN selection policy(WLANSP) rules. For example, a UE may have valid rules from both HPLMNand VPLMN, when it is roaming.

In this case, the UE may be configured to use WLANSP rule provided byHPLMN to determine if there is available WLAN access network(s). Forexample, referring to FIG. 8 which depicts simultaneous connectivity tomultiple VPLMNs, if a UE has different VPLMN in 3GPP access and WLANaccess, the UE could not use the V-ANDSF in VPLMN1 or VPLMN2, but shoulduse the H-ANDSF. In this case, if there is available WLAN accessnetwork(s) according to WLANSP rule provided by HPLMN, then the UEattempts to connect to the available WLAN access network. If there is noavailable WLAN access network(s) according to WLANSP rule provided byHPLMN, then the UE may refer to WLANSP rule provided by the VPLMN todetermine if there is available WLAN access network(s). Here, a casethat there is no available WLAN access network(s) according to WLANSPrule provided by HPLMN may include a case that the UE requests toconnect to a WLAN access network selected according to WLANSP ruleprovided by HPLMN but rejected (or refused, or failed) by a networknode. A list of excluded or prohibited WLAN access network(s) may beincluded in the rejection message, and the UE may update the WLANSP rulewith the list of excluded or prohibited WLAN access network(s). Here,the UE may basically use the WLANSP provided by HPLMN withusing/reflecting/incorporating the WLANSP provided by VPLMN (especiallyusing/reflecting/incorporating the list of excluded or prohibited WLANaccess network(s)) to check for available WLAN access network(s). Inother words, the WLANSP provided by HPLMN may be updated based on thelist of excluded or prohibited WLAN access network(s) provided by VPLMN.Then the UE may check if there are available WLAN access network(s)based on the updated WLANSP rule (i.e., taking into account the list ofexcluded or prohibited WLAN access network(s)).

Additionally or alternatively, the UE may be configured to use WLANSPrule provided by VPLMN. The UE may use WLANSP rule provided by the VPLMNto determine if there is available WLAN access network(s). Here, theWLANSP rule provided by the VPLMN may include a list of excluded orprohibited WLAN access network(s).

The above embodiments are described with examples that a WLAN accessnetwork is a forbidden access or a restricted access, but the scope ofthe invention is not limited thereto. The above embodiments may beapplicable to various granularity or various forms of WLAN accessnetwork classification, such as a limited access, a prohibited access,an excluded access, a non-recommended access.

The policies described above may include various policies not onlydefined in TS 23.402, TS 24.302, TS 24.312, but also will be defined inthe future (e.g., policy including Hotspot 2.0 related information).

FIG. 10 is a flow diagram illustrating an exemplary method for accessnetwork selection in visited network according to the present invention.

In the example of FIG. 10, it is assumed that UE may be configured withmultiple valid WLAN selection policy (WLANSP) rules. For example, a UEmay have valid rules from both a home network (e.g., HPLMN) and avisited network (e.g., VPLMN), when it is in a visited network (i.e., inroaming).

In step S10, the UE may determine if there is an available WLAN accessnetwork in the visited network. Here, the UE may be configured to use aWLANSP of the HPLMN for the determining step of S10. For example, the UEhas simultaneous connectivity to multiple VPLMNs as in the example ofFIG. 8, and has different VPLMN in 3GPP access and WLAN access, then theUE could not use the WLANSP provided by the V-ANDSF of VPLMN in 3GPPaccess or the WLANSP provided by the V-ANDSF of VPLMN in WLAN access,but should use the WLANSP provided by the H-ANDSF.

In step S20, the UE may update a WLANSP with a list of excluded (orforbidden, or restricted) WLAN access network(s) or with the selectedWLAN access network but rejected, if the selected WLAN access network inthe VPLMN is not available. Here, the WLANSP being updated in step S20is basically a WLANSP of the HPLMN. In addition, the list of excludedWLAN access network(s) is provided by the VPLMN.

It may be determined that the selected WLAN access network in the VPLMNis not available, if a request of the UE for connecting to the selectedWLAN access network in the VPLMN is rejected by the VPLMN. The UE mayreceive a rejection message from the VPLMN, if the request forconnecting to the selected WLAN access network in the VPMN is rejected.The list of excluded WLAN access network(s) may be included in therejection message, or may be provided to the UE by the V-ANDSF.

In step 30, the UE may re-determine if there is an available WLAN accessnetwork in the VPLMN based on the updated WLAN selection policy. Then,the UE may request a connection/association/access to a proper WLANaccess network (i.e., a WLAN access network not matching the list ofexcluded WLAN access network(s)).

The exemplary method of FIG. 10 is described as a series of steps forclarity, but it is not a limitation of order of the steps and all orsome of the steps may be performed simultaneously or in a differentorder. Further, not all of the steps described in the figures arenecessary for implementing a scheme proposed by the present invention.

According to the embodiments of the present invention, efficient usageof network resources and enhanced user experiences are provided.

The above-described embodiments of the present invention may beindependently applied or two or more of the above-described embodimentsmay be simultaneously applied.

FIG. 11 is a diagram showing the configuration of an apparatus accordingto an exemplary embodiment of the present invention.

Referring to FIG. 11, the apparatus 1000 according to the presentinvention may include a transceiving module 1010, a processor 1020 and amemory 1030. The transceiving module 1010 may be configured to transmitvarious signals, data and information to an external device (e.g., anetwork node, UE, a server, etc.) and receive various signals, data andinformation from an external device (e.g., a network node, UE, a server,etc.). The processor 1020 may control overall operation of the apparatus1000 and the apparatus 1000 may be configured to perform a function forprocessing information transmitted or received to or from an externaldevice. The memory 1030 may store the processed information for apredetermined time and may be replaced by a buffer (not shown).

The apparatus 1000 may be implemented as a UE described in the presentdocument. The processor 1020 may be configured to determine if there isan available WLAN access network in the visited network. The processor1020 may be further configured to update a WLAN selection policy with alist of excluded WLAN access network(s), if the selected WLAN accessnetwork in the VPLMN is not available. The processor 1020 may be furtherconfigured to re-determine if there is an available WLAN access networkin the visited network based on the updated WLAN selection policy.

The embodiments of the present invention may be independently orsimultaneously applied to the detailed configuration of the apparatus1000 and descriptions thereof will be omitted for clarity.

The embodiments of the present invention may be implemented by a varietyof means, for example, hardware, firmware, software, or a combinationthereof.

In the case of implementing the present invention by hardware, thepresent invention may be implemented with application specificintegrated circuits (ASICs), Digital signal processors (DSPs), digitalsignal processing devices (DSPDs), programmable logic devices (PLDs),field programmable gate arrays (FPGAs), a processor, a controller, amicrocontroller, a microprocessor, etc.

If operations or functions of the present invention are implemented byfirmware or software, the present invention may be implemented in theform of a variety of formats, for example, modules, procedures,functions, etc. Software code may be stored in a memory unit so that itmay be driven by a processor. The memory unit is located inside oroutside of the processor, so that it may communicate with theaforementioned processor via a variety of well-known parts.

The detailed description of the exemplary embodiments of the presentinvention has been given to enable those skilled in the art to implementand practice the invention. Although the invention has been describedwith reference to the exemplary embodiments, those skilled in the artwill appreciate that various modifications and variations may be made inthe present invention without departing from the spirit or scope of theinvention described in the appended claims. For example, those skilledin the art may use each construction described in the above embodimentsin combination with each other. Accordingly, the invention should not belimited to the specific embodiments described herein, but should beaccorded the broadest scope consistent with the principles and novelfeatures disclosed herein.

The aforementioned embodiments are achieved by combination of structuralelements and features of the present invention in a predeterminedmanner. Each of the structural elements or features should be consideredselectively unless specified separately. Each of the structural elementsor features may be carried out without being combined with otherstructural elements or features. Also, some structural elements and/orfeatures may be combined with one another to constitute the embodimentsof the present invention. The order of operations described in theembodiments of the present invention may be changed. Some structuralelements or features of one embodiment may be included in anotherembodiment, or may be replaced with corresponding structural elements orfeatures of another embodiment. Moreover, it will be apparent that someclaims referring to specific claims may be combined with other claimsreferring to the other claims other than the specific claims toconstitute the embodiment or add new claims by means of amendment afterthe application is filed.

It will be apparent to those skilled in the art that variousmodifications and variations may be made in the present inventionwithout departing from the spirit or scope of the inventions. Thus, itis intended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

The embodiments of the present invention are applicable to variousmobile communication systems.

What is claimed is:
 1. A method for selecting a Wireless Local AreaNetwork (WLAN) access network by a user equipment (UE) in a visitednetwork, the method comprising: determining, by the UE, if a selectedWLAN access network in the visited network is available; updating, bythe UE, a WLAN selection policy with a list of excluded WLAN accessnetwork, if the selected WLAN access network in the visited network isnot available; and re-determining, by the UE, if there is an availableWLAN access network in the visited network based on the updated WLANselection policy.